In this article, we will discuss how to do Multiple criteria aggregation on PySpark Dataframe.
Data frame in use:
In PySpark, groupBy() is used to collect the identical data into groups on the PySpark DataFrame and perform aggregate functions on the grouped data. So by this we can do multiple aggregations at a time.
Syntax:
dataframe.groupBy(‘column_name_group’).agg(functions)
where,
- column_name_group is the column to be grouped
- functions are the aggregation functions
Lets understand what are the aggregations first. They are available in functions module in pyspark.sql, so we need to import it to start with. The aggregate functions are:
- count(): This will return the count of rows for each group.
Syntax:
functions.count(‘column_name’)
- mean(): This will return the mean of values for each group.
Syntax:
functions.mean(‘column_name’)
- max(): This will return the maximum of values for each group.
Syntax:
functions.max(‘column_name’)
- min(): This will return the minimum of values for each group.
Syntax:
functions.min(‘column_name’)
- sum(): This will return the total values for each group.
Syntax:
functions.sum(‘column_name’)
- avg(): This will return the average for values for each group.
Syntax:
functions.avg(‘column_name’)
We can aggregate multiple functions using the following syntax.
Syntax:
dataframe.groupBy(‘column_name_group’).agg(functions….)
Example: Multiple aggregations on DEPT column with FEE column
Python3
# importing module import pyspark # importing sparksession from pyspark.sql module from pyspark.sql import SparkSession #import functions from pyspark.sql import functions # creating sparksession and giving an app name spark = SparkSession.builder.appName('sparkdf').getOrCreate() # list of student data data = [["1", "sravan", "IT", 45000], ["2", "ojaswi", "CS", 85000], ["3", "rohith", "CS", 41000], ["4", "sridevi", "IT", 56000], ["5", "bobby", "ECE", 45000], ["6", "gayatri", "ECE", 49000], ["7", "gnanesh", "CS", 45000], ["8", "bhanu", "Mech", 21000] ] # specify column names columns = ['ID', 'NAME', 'DEPT', 'FEE'] # creating a dataframe from the lists of data dataframe = spark.createDataFrame(data, columns) # aggregating DEPT column with min.max,sum,mean,avg and count functions dataframe.groupBy('DEPT').agg(functions.min('FEE'), functions.max('FEE'), functions.sum('FEE'), functions.mean('FEE'), functions.count('FEE'), functions.avg('FEE')).show() |
Output:
Example 2: Multiple aggregation in grouping dept and name column
Python3
# importing module import pyspark # importing sparksession from pyspark.sql module from pyspark.sql import SparkSession #import functions from pyspark.sql import functions # creating sparksession and giving an app name spark = SparkSession.builder.appName('sparkdf').getOrCreate() # list of student data data = [["1", "sravan", "IT", 45000], ["2", "ojaswi", "CS", 85000], ["3", "rohith", "CS", 41000], ["4", "sridevi", "IT", 56000], ["5", "bobby", "ECE", 45000], ["6", "gayatri", "ECE", 49000], ["7", "gnanesh", "CS", 45000], ["8", "bhanu", "Mech", 21000] ] # specify column names columns = ['ID', 'NAME', 'DEPT', 'FEE'] # creating a dataframe from the lists of data dataframe = spark.createDataFrame(data, columns) # aggregating DEPT, NAME column with min.max, # sum,mean,avg and count functions dataframe.groupBy('DEPT', 'NAME').agg(functions.min('FEE'), functions.max('FEE'), functions.sum('FEE'), functions.mean('FEE'), functions.count('FEE'), functions.avg('FEE')).show() |
Output:
